The invention relates to a dual mode phone capable of establishing a connection to at least one cellular network or at least one cordless network, said phone continuously monitoring system information messages from said at least one cellular network and said at least one cordless network to maintain an idle mode connection.
Users demand long standby times, because they find it cumbersome to have to recharge their portable telephone more than a couple of times a week. The manufacturers have worked intensely on reducing the energy consumption which is of no use to the user. Portable cellular telephones have many advantages, as they offer great mobility, which also applies to data transmission, good speech quality and good data safety (which applies to digital systems in particular).
If the advantages of cellular networks are to be utilized in office environments and the like, this may take place e.g. via cordless systems, such as DECT. To avoid having to equip the staff with both a cordless telephone and a cellular telephone, it is attempted to integrate the two types in a so-called dual mode telephone, where the telephone in idle mode (ready to receive ingoing calls and to establish outgoing calls) continuously monitors the system information messages of the two networks. This requirement of continuous monitoring may have as a result that the telephone consumes energy in searching for a network, e.g. the DECT network, even though the telephone is outside the area covered by the network.